Effect of solder void on mechanical and thermal properties of flip-chip light-emitting diode: Statistical analysis based on finite element modeling.

With the increasing demand for highly efficient lighting in the automotive industry, flip-chip light-emitting diodes (LEDs) have become widely used for both interior and exterior lighting. Solder, serving as a crucial interconnecting material, often develops voids during the reflow process, compromising the integrity and reliability of the connections. Thus, understanding the impact of these voids on the mechanical and thermal properties of the product is vital for improving reliability accuracy. This work employs computational methods alongside experimental approaches to address the challenges of replicating solder voids and controlling the solder void fraction. A comprehensive study investigates the effects of solder voids on shearing properties and thermal conductance. Random voids were introduced into the solder pads of an LED assembly within a finite element model (FEM), leading to predictions of maximum shear stress and LED junction temperature. The findings correlate well with the experimental data, validating the FEM's applicability. Furthermore, a statistical analysis was conducted to explore the relationship between solder void fraction, position, and size, aiming to provide objective guidelines for analyzing soldered assembly tomography in reliability assessments.

Fenoldopam Mesylate Enhances the Survival of Mesenchymal Stem Cells Under Oxidative Stress and Increases the Therapeutic Function in Acute Kidney Injury.

Mesenchymal stem cells (MSCs) have gained interest as an alternative therapeutic option for renal diseases, including acute kidney injury (AKI). However, their use is often limited owing to low survival rates in vivo. Fenoldopam mesylate (FD) is a selective dopamine D1 receptor agonist with antioxidative and anti-apoptotic roles. Herein, we investigated whether FD can enhance the survival of MSCs undergoing oxidative stress in vitro. In addition, the therapeutic effect of MSCs and FD-treated MSCs (FD-MSCs) was compared in a mouse model of AKI induced by cisplatin. The survival of MSCs under oxidative stress was augmented by FD treatment. FD induced the phosphorylation of cAMP response element-binding protein and AKT, contributing to enhanced growth compared with untreated MSCs. The expression of nuclear factor erythroid-2-related factor 2 (NRF2) and heme oxygenase-1 was increased by FD treatment, and nuclear translocation of NRF2 was found exclusively in FD-MSCs. FD downregulated BAX expression, increased the mitochondrial membrane potential, reduced reactive oxygen species generation, and decreased the apoptotic death of MSCs induced by oxidative stress. Moreover, renal function and tubular injury were improved in FD-MSCs compared with non-treated MSCs. Furthermore, tubular injury, apoptosis, and macrophage infiltration, as well as the serum level of tumor necrosis factor-α were reduced, while tubular cell proliferation was markedly increased in FD-MSCs compared with MSCs. Our study demonstrated that FD increases the survivability of MSCs in an oxidative environment, and its use may be effective in preparing robust therapeutic MSCs.

Cellhesion VP enhances the immunomodulating potential of human mesenchymal stem cell-derived extracellular vesicles.

Mesenchymal stem cell (MSC) transplantation is a promising therapy for regenerative medicine. However, MSCs grown under two-dimensional (2D) culture conditions differ significantly in cell shape from those in the body, with downregulated stemness genes and secretion of paracrine factors. Here, we evaluated the effect of 3D culture using Cellhesion VP, a water-insoluble material composed of chitin-based polysaccharide fibers, on the characteristics of human Wharton's jelly-derived MSCs (hMSCs). Cellhesion VP significantly increased cell proliferation after retrieval. Transcriptome analyses suggested that genes involved in cell stemness, migration ability, and extracellular vesicle (EV) production were enhanced by 3D culture. Subsequent biochemical analyses showed that the expression levels of stemness genes including OCT4, NANOG, and SSEA4 were upregulated and migration capacity was elevated in 3D-cultured hMSCs. In addition, EV production was significantly elevated in 3D cells, which contained a distinct protein profile from 2D cells. Gene and drug connectivity analyses revealed that the 2D and 3D EVs had similar functions as immunomodulators; however, 3D EVs had completely distinct therapeutic profiles for various infectious and metabolic diseases based on activation of disease-associated signaling pathways. Therefore, EVs from Cellhesion VP-primed hMSCs offer a new treatment for immune and metabolic diseases.